(1) Field of the Invention
The present invention lies in the field of communications systems. It relates to a method of simultaneously transforming voice signals input to a communications system. The method is intended more particularly for the communications systems present in aircraft.
(2) Description of Related Art
At present, in the field of aviation in general, and in the field of rotary wing aircraft more particularly, a pilot uses the communications system of the aircraft to dialog with multiple remote parties, whether outside the aircraft or indeed on board the aircraft.
The pilot needs to communicate with air traffic controllers in various control towers controlling and organizing the traffic of aircraft, and also with the pilot of other aircraft or indeed with remote parties on the ground, on board a ship, or on board an oil platform, for example.
The communications system of an aircraft can receive a plurality of voice signals, each voice signal being made up of waves that are received at a given reception frequency. Each received voice signal is then transmitted to the pilot by the communications system in the form of the voice of the remote party. The term “input voice signal” is used to mean a signal received by the communications system and corresponding to the voice of a remote party in communication with the pilot.
For example, high frequency (HF), very high frequency (VHF), or indeed ultra-high frequency (UHF) systems are known for performing such communication.
In order to undertake this type of communication, the pilot makes use of appropriate adjustment means on the communications system to define one or more reception frequencies. Each reception frequency corresponds to the frequency of the waves making up each voice signal corresponding to the voices of the remote parties in communication with the pilot.
Below in the present description, the term “reception frequency of the signal” is used more simply to designate the frequency of the waves making up the received signal.
The pilot also communicates with people on board the aircraft, such as a copilot, a navigator, or any other person on board the aircraft. The communications system making this possible is sometimes referred to as an “on-board telephone”.
Nowadays, the communications systems present on aircraft enable signals to be received simultaneously on a plurality of reception frequencies, thus making it possible to communicate simultaneously with a plurality of remote parties such as a traffic controller, or the pilot of another aircraft. In addition, the people on board the aircraft use the same communications system, via the on-board telephone to communicate with one another and with the pilot of the aircraft.
A problem then arises when several remote parties, whether external to the aircraft or on board it, speak simultaneously to the pilot. Since the voices of the remote parties are then superposed, their intelligibility is reduced significantly, and understanding messages becomes more complicated.
Furthermore, when the pilot is already in communication with one remote party, another message received on another reception frequency can be difficult to understand or even inaudible. That other message might be important, e.g. coming from a traffic controller requesting the pilot of the aircraft to change course, and the message might be misunderstood or not understood at all, and therefore not taken into account by the pilot of the aircraft.
In order to mitigate such problems with present communications systems, the pilot of an aircraft can manually increase the sound volume associated with the reception frequency for a signal that corresponds to the poorly understood message. Conversely, the pilot can lower the sound volume associated with the reception frequency corresponding to messages that are considered as not having priority.
Either way, the pilot temporarily lets go of the flight controls in order to modify the sound volume associated with the reception frequency(ies) of the corresponding signal(s), and that might be dangerous, depending on flying conditions. Furthermore, during the time it takes to change sound volume, some or all of the messages might be poorly understood or even not understood at all by the pilot. This can be dangerous, depending on the importance of the message, particularly if the pilot needs to perform a maneuver or to take action very quickly.
Finally, the pilot may ask the remote party to repeat the message that has not been understood or that has been poorly understood. Once again, that can be dangerous if it is necessary for the pilot to maneuver or to take action very quickly.
Under all circumstances, pilot reactivity is degraded by the received message being poorly understood or not understood at all, and the loss of time this causes can be dangerous if the message is particularly important and rapid reaction is needed.
Nevertheless, if the aircraft has a system for spatializing communications, understanding various superposed messages can be made easier. For example, according to document U.S. Pat. No. 5,438,623, such a system makes it possible to transmit the received messages so as to give the impression that they come from different sources placed in different locations in the space around the pilot. However, there is no priority amongst the various messages depending on the remote party, e.g. a traffic controller. There is no transformation of the signal, but merely a shift in the time the message is perceived, thereby giving the impression of the source of the corresponding voice being shifted in three-dimensional space.
Nevertheless, as from about three or four simultaneous messages, the pilot once more perceives voices that are superposed and very difficult to understand, since the spatialization is no longer sufficient for improving the situation.
There also exists systems for mitigating poor hearing of a user. Such systems, e.g. described in documents EP 2 138 009 and US 2002/0111796, serve to modify the characteristics of a voice so as to make it easier to understand by a user having a hearing defect. The characteristics of the voice that are modified include sound volume and one or more frequencies of the voice.
A voice may be resolved into a plurality of tones, each tone being characterized in particular by its frequency. For example, a tone with a low frequency corresponds to a low-pitch tone and a tone with a high frequency corresponds to a high-pitch tone.
By increasing the frequency of one or more tones making up the voice, it is possible to make it higher pitched, and consequently more distinctive for certain people.
However, the systems described modify one voice only and they are not capable of processing a plurality of voices simultaneously.
Elsewhere, the document “Design considerations for improving the effectiveness of multitalker speech displays”, from the Proceedings of the 2002 International Conference on Auditory Display, Kyoto, JP, of Jul. 2, 2002, describes various characteristics that contribute to the intelligibility or lack of intelligibility associated with superposed voices during multitalker communications, which characteristics may be background sounds, the number of talkers, whether or not a talker is known, the characteristics that are intrinsic to each voice, the sound level of each voice, or indeed the spatial position of each voice. That document also mentions that it is possible to modify one or more characteristics of a voice in order to improve its intelligibility, but nevertheless, it does not disclose how those characteristics are to be modified.
The technological background also contains the documents “A review of the cocktail party effect” from Journal of the American Voice I/O Society, 1992, Vol. 12, pp. 35-50, “Aesthetic and auditory enhancements for multi-stream information sonification” from Proceedings of the 3rd International Conference on Digital Interactive Media Entertainment and Arts, 2008, pp. 224-231, and “Monitoring the simultaneous presentation of spatialized speech signals in a virtual acoustic environment” from Defense Technical Information Center OAI-PMH Repository, US, Jun. 1, 1998, and also document U.S. Pat. No. 5,438,623.
In the description below, the term “frequency of the voice” is used to designate simply the frequencies of the tones making up the voice. These voice frequencies are completely distinct and independent from the frequency on which the signal corresponding to the voice is received.